In a semiconductor device, a sudden change in power supply current due to start or stop of operations of multiple circuit blocks may cause a power supply noise in some cases. To address this, a technique of reducing the occurrence of a power supply noise is proposed, in which a semiconductor device is caused to consume approximately the same power by operating, in accordance with a change in the power supply current, unused latch circuits which are not involved in the operation of the semiconductor device (for example, see Japanese Laid-open Patent Publication No. 11-296268). Moreover, a technique of gradually changing the frequency of a clock when starting or stopping the supply of the clock to a clock synchronization circuit is proposed so that a sudden change in the power supply current is reduced and the occurrence of a power supply noise is reduced (for example, see Japanese Laid-open Patent Publications No. 4-321318 and No. 2004-13820).
However, the number of unused latch circuits is determined depending on the design of each semiconductor device, so that the technique of reducing the occurrence of a power supply noise by operating the unused latch circuits is applicable only to limited semiconductor devices.
A semiconductor device and a method of controlling the semiconductor device discussed herein are aimed to reduce the occurrence of a power supply noise by utilizing a latch circuit to be used for implementing a function of the semiconductor device.